確かにInternal Server Errorは解消された。
でもなんでこんなことに?
理由をたずねてみた。
その返事がこれ
The issue reported was caused by a wrong permission that was set on your .htaccess file causing the PHP script not to be rendered by the engine as they should. The permissions of the .htaccess file have been set to 644 and at this point everything is working as expected.
そんなことってあるのかな???